1. Field of the Invention
The present invention relates to a disk array apparatus, and more specifically, to a disk array apparatus in which a firmware of a disk device can be updated even when the disk array apparatus is in an operation state (being online).
2. Related Art
A disk array apparatus, in which a plurality of disk devices (hereinafter, “disk device” may be called as “HDD”, including a disk controller thereof) are arranged for providing redundancy, to expand a storage capacity, increase an information transmission speed, and enhance reliability, have come into widespread use. Each of the plurality of disk devices (HDDs) performs information transmission/reception with a host computer (server) via a disk array control apparatus, and, seen from the host computer, disk devices appear as a single disk device, virtually. As a technique to realize the disk array apparatus which can provide an enlarged storage capacity, a higher transmission speed of information, and enhanced reliability, RAID (Redundant Array of Inexpensive Disks) systems have been widely employed. As a type of the RAID systems, a RAID-0 system is optimized for providing higher transmission speed with no redundancy. However, RAID-1 to RAID-5 systems are widely known to be configured to provide redundancy, with which a disk array apparatus can continue to operate even when one of the HDDs fails.
Meanwhile, in the disk array apparatus, each disk device (HDD), as well as the disk array control apparatus, is provided with a CPU (processing unit) and software for controlling the disk mechanism (hardware). This software is resident in a ROM (nonvolatile memory) and the like, organizes the control action of the hardware such as a disk mechanism portion mainly, thus the software is called as “firmware (HDD control firmware)”. The firmware has a characteristic of being updated according to certain reasons, such as version-upgrade, for example.
Generally, the firmware update (referred to as “download,” in many cases) is performed by the manner in which an update firmware is transferred from the disk array control apparatus to the HDD side. However, since the control action of the HDD is organized by the firmware as described above, an operation of an HDD whose firmware is to be updated have to be stopped temporarily during updating the firmware in general, and this may cause a stoppage of the disk array apparatus, and further, an interruption of service, etc.
Thus, there is proposed a system with which it is possible to download an HDD control firmware to an HDD (update the HDD) without stopping the operation of a disk array apparatus even when the operation of a disk device (HDD) is stopped (Japanese Unexamined Patent Publication 11-353127: Patent Document 1). That is, with this system, all of recorded contents of a target HDD whose firmware is to be updated is copied to a cache (or a spare disk device), the cache is controlled so as to form an array with the other disk devices, then a firmware stored in a spare disk device or the like is downloaded to the target HDD which is to be updated, and after completion of the download, the content of the target HDD is renewed with the data stored in the cache.
With this system, however, since it is required to copy all of the contents recorded in the target HDD to the cache before the firmware update, it takes an unnecessary time, and further, the cache needs to have the same capacity as that of the HDD.
As a problem of the traditional technique described above, in general, the operation of the target disk device is forced to be stopped temporarily for updating, and this has been a cause of deterioration of the operating capacity of the system and quality of service, which means, a stoppage of the disk array apparatus and an interruption of the service, and the like.
Meanwhile, there has been another traditional technique which enables a firmware to be downloaded to an HDD without stopping the operation of a disk array apparatus, in which the target HDD is disconnected, and a cache (or a disk device) is prepared as a substitution thereof. With this method, however, there has been operational constraint such that it is required to copy all of the contents recorded in the target HDD to be updated to the cache before the firmware update, thus time is wasted for this operation, and further, the cache needs to have a large capacity which is equivalent to the capacity of the HDD.
Japanese Unexamined Patent Publication 2002-318666 (Patent Document 2) discloses a technique with which firmware can be updated for a plurality of disk devices without stopping the operation of a disk array apparatus. Patent Document 2 discloses a configuration in which, written data in a target disk device whose firmware is to be updated are copied to a disk device other than the target disk device to be updated for saving, and when the firmware update of the target disk device is complete, the saved data are rewritten into the disk device whose firmware is updated.
With the technique disclosed in Patent Document 2, operation of the disk array apparatus is not required to be stopped, but it is necessary to save the data written in the target disk device whose firmware is to be updated by copying the data to a disk device other than the target disk device to be updated, and it takes a time for copying the data.